which diagram best illustrates the magnetic field of a bar magnet?

Answer:

The magnetic field lines of a bar - magnet start from the north pole (N) and end at the south pole (S) outside the magnet and form closed loops. So, the diagram with field - lines starting from the N pole and ending at the S pole outside the magnet is the correct one. Since the two diagrams you provided seem identical in terms of the basic magnetic - field - line representation for a bar magnet (assuming they both have field lines starting from N and ending at S outside the magnet), both would be correct if they follow this rule. If there are differences not visible in the provided image, the one with field lines starting from N and ending at S outside the magnet is the answer.

Explanation:

Step1: Recall magnetic field line property

Magnetic field lines start from N and end at S outside magnet.

Step2: Check the diagrams

Verify if field lines follow the rule.